The version used by the USAF was the UH-1F. It used surplus engines from USAF HH-3s, which had a turned exhaust. The exhuast exited out the right side of the upper fuselage. It also had the longer tail boom and rotors from a UH-1D, the version Scorpiomikey posted above. The tail boom is measured from the seam where it connects to the fuselage just below the engine area.
As to camo, no, each crew could not modify the standard scheme. It was set out in a manual the exact way to paint the camo. The USAF camo on most of them was called the SEA (South East Asia) scheme of dark green, medium green, and dark tan over an off-white underside. Stateside UH-1Fs were also painted overall grey, some were also overall dark blue.
Here are a few examples.
The longer tail boom allowed for a baggage compartment on the right side near the fuselage. You can see it in the below pic.
Converting it into a UH-1F is a major conversion, but can be done. If you search the site, there are a couple examples of it being done. Good luck.
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